Polyvinyl chloride composition

ABSTRACT

Polyvinyl halide extrusion-blow molding compositions containing calcium-magnesium-zinc stabilizers are improved by the addition of long chain alcohols and esters of long chain hydroxy acids. Clear rigid film and containers of improved clarity and freedom from yellowness, when extruded and blow molded at normal temperatures, are produced.

Ellie King iees Paiwi [54] POLYVINYL CHLORHDE COMPOSITION [72] Inventor: Laurence E. King, Mooretown, Ontario,

[52] US. Cl. ..260/23 XA, 260/45.7 P, 260/4575 R,

260/4585, 260/4595, 260/899 [51] Int. Cl ..C08f 29/18, C08f45/62 [58] Field of Search ..260/23 XA, 45.75 R, 45.85

[56] References Cited UNITED STATES PATENTS 2,387,571 10/1945 Fikenstscher et al ..260/45.95 3,054,771 9/ 1962 I-Iiestand et a1 ..260/23 2,274,555 2/1942 Japs ....260/45.85 3,069,400 12/1962 Halpem ..260/87.5 3,167,533 1/1955 Donat ..260/86.3 2,156,956 5/1939 Agens ..260/45.85

OTHER PUBLICATIONS Smith, Stabilizers for Vinyl Polymers" British Plastics, May 1954 pages 176-179 Cox ..260/45.85 X

Jankowiak et al. ..260/45 .85 X Zaremsky ..260/23 Primary Examiner-Donald E. Czaja Assistant Examiner-Donald J. Barrack Attorney-Chasan & Sinnock and Harold Einhom [57] ABSTRACT Polyvinyl halide extrusion-blow molding compositions containing calcium-magnesium-zinc stabilizers are improved by the addition of long chain alcohols and esters of long chain hydroxy acids. Clear rigid film and containers of improved clarity and freedom from yellowness, when extruded and blow molded at normal temperatures, are produced.

4 Claims, 3 Drawing Figures P'A'TE'N'TEDJUL 4 1972 FIGURE l EFFECT OF ALCOHOLS ON MILL STABILITY OF POLYMER A YELLOWNESS INDEX VS. TIME Temperature 375F YELLOWNESS 5 INDEX CURVE menacin- ALCOHOL NONE I- C 3phr 20 2-CI2 u I-CM a TIME, MINUTES Laurence E King INVENTOR BY ATTORNEY P'ATENTEDJUL -4 1972 SHEET 2 [IF 3 FIGURE 2 YELLOWNESS INDEX VS. TIME Temperature 375F r h L p n" 0 H 0 O mzmmm M CCCC A lll| E V Dn 23456 U C 5 5 5 5 l. 2 m 69 TIME, MINUTES Laurence E King INVENTOR BY ATTORNEY PATENTEDJUL 4 m2 3, 674, 730

SHEET 3 OF 3 FIGURE 3 EFFECT OF METHYL HYDROXY STEARATES ON MILL STABILITY OF POLYMER A YELLOWNESS INDEX VS. TIME Temperature 375F CURVE ESTER l NONE I75 2 l7-0H 3phr 3 lZ-OH l 4 OC-OH u 5 l2-OH 2phr added during polymerization 6 9,|0 di-OH 3phr x Lu 0 Z m m m z 3 3 .1 Lu |o 5 I I I I I O l 2 3 4 5 TIME, MINUTES Laurence F. King INVENTOR BY ATTORNEY i OlLYVliNYlL CHLQRKDE COWUSII'IIIQN THE PRIOR ART it is generally known that severe exposure of such resinous materials as polyvinyl chloride and copolymers thereof to heat and/or light brings about discoloration, brittleness and loss of strength. Exposure to high temperatures frequently occurs during fabrication of the material, and exposure to light may occur throughout the life of the material. Numerous attempts have been made in the prior art to introduce stabilizers which will reduce or eliminate these deleterious effects on the polymer. Organotin compounds, because of their unusual heat stabilizing properties, are normally required in polyvinyl chloride extrusion-blow molding compositions in order to produce the best color and clarity in bottles, film, etc. However, for food packaging applications, organotin compounds have the disadvantage in generally being quite toxic. Two exceptions include di(n-octyl) tin maleate and di-octyl tin SS bis (iso-octyl mercaptoacetate). These are the only tin stabilizers currently approved for food use in the United States and Canada. Because these materials are extremely costly, it has been found desirable to find alternative stabilizers. Therefore, conventional calcium-zinc or magnesium-zinc stabilizers have generally been employed.

Great difficulties are encountered in producing bottles, film, etc., of good color and clarity when using these conventional stabilizers. Blue or violet toners mask the yellowing ten dency to a limited extent but reduce the clarity when used in large enough amounts to be effective. Therefore, it has been .found necessary to use additives in combination with these stabilizers to produce the desired results. To withstand processing temperatures of PVC without volatilization the additives should have boiling points in excess of 450 F. Additives which have been employed in the prior art include borate esters of polyhydric alcohols, epoxy-containing organic materials in combination with unsaturated esters of polycarboxylic acids, polyhydric primary aliphatic alcohols containing at least three hydroxy groups, aliphatic acid esters of polyhydric alcohols, etc. It has heretofore been considered necessary when employing alcohols as additives to have at least two, and preferably more, hydroxy groups present in a molecule.

THE PRESENT INVENTION .It has now been discovered that it is possible to use compounds selected from the group consisting of alcohols having a single hydroxy group and esters of long chain mono-or dihydroxy acids in combination with a mixture of the calcium, magnesium and zinc salts of organic acids as the stabilizing agent for vinyl halide polymers. The use of such a combination results in excellent heat stability for the polymer at processing temperatures as high as 400 F. The good processability is due mainly to a marked plasticizing or internal lubricating effect of these alcohols or esters on the particles in the polymer matrix, an effect which is evidenced by a lowering of the glass transition temperature and the melt viscosity of the polymer. Further, the color clarity of the product compares favorably with that obtained using the systems of the prior art. This is due to the employment of the three-component stabilizer system calcium, magnesium and zinc together with a long chain alcohol or ester. Since these alcohols and esters are non-toxic, products prepared using the present technique are readily adaptable for use in food packaging.

The vinyl halide polymers useful in the present invention include polyvinyl chloride, polyvinylidene chloride, copolymers containing vinyl chloride in a major proportion with other copolymerizable monomers such as vinyl formate, vinyl acetate, propylene, ethylene, butylenes, alkyl vinyl ethers, alkyl acrylates and methacrylates, alkyl maleates, alkyl fumarates, etc. The weight average molecular weight of the polyvinyl halide resin is in the range of about 50,000 to about 100,000, and preferably from about 65,000 to about 75,000.

The alcohols to be utilized as stabilizers in the process of this invention are alcohols having the following formula:

wherein R is a (I -C straight chain alkyl group and R is hydrogen or a C -C straight chain alkyl group, provided that if R is hydrogen R must be at least C That is, acceptable alcohols include primary and secondary aliphatic alcohols having a carbon number of at least 12 and not exceeding 45. Preferably, the carbon number range will be from 12 to 24. Examples of alcohols which are useful in the present invention include but are not limited to l-dodecanol, 2-dodecanol, ltetradecanol, l-hexadecanol, l-octadecanol, l-eicosanol (C20) and higher molecular weight wax alcohols up to C Preferably, the alcohol to be used will be one of the following: l-tetradecanol, l-hexadecanol, l-octadecanol and leicosanol.

The esters of long chain hydroxy acids applicable to the instant invention have the following formula:

wherein X is hydrogen or a C,C straight chain alkyl group, L is C to a C straight chain alkyl group, and M is a C to C alkyl group. Preferably, K is hydrogen to a C alkyl group, L is C to a C alkyl group, and M is a C to C alkyl group. Esters falling within the scope of the above formula include methyl tit-hydroxy stearate, ethyl l2-hydroxy stearate, butyl l7- hydroxy stearate, alkyl 9,10-dihydroxy stearates, amyl hydroxy laurates, propyl hydroxy myristates, methyl hydroxy palmitates, butyl hydroxy docosanoates. Examples of preferable esters include but are not limited to methyl cur-hydroxy stearate, methyl l2-hydroxy stearate, methyl l7-hydroxy stearate and methyl 9,10-dihydroxy stearate.

The organic acids from which the complex calcium, magnesium and zinc salts may be derived are monocarboxylic acids, including aliphatic acids having at least six carbon atoms, aromatic acids, thio-acids, sulphonic acids and naphthenic acids. Specific examples include lauric acid, stearic acid, oleic acid, ricinoleic acid, benzoic acid, salicylic acid, phenyl acetic acid, diphenolic acid, thio-glycollic acid, maleic acid, naphthenic acid, erucic acid. Preferably, the acid will be selected from one of the following: stearic acid, ricinoleic acid, oleic acid, naphthenic acid.

A typical formulation for the vinyl halide polymer used in the practice of this invention consists of parts of the vinyl halide polymer; 5-20 parts, preferably 15 parts, of an impact modifier such as e.g. acrylonitrile-butadiene styrene terpolymers, nitrile rubbers, methyl methacrylate butadienestyrene terpolymers, etc.; and the stabilizer system of the instant invention wherein the hydroxy compound is present in from 1 to 10 parts, and preferably 2 to 4 parts, the calcium salt is present in proportions of about 0.01 to about 0.2 parts by weight, preferably 0.02 to 0.1 parts, the magnesium salt is present in proportions of about 0.1 to about 1.0 parts, preferably 0.2 to 0.6 parts, and the zinc salt is present in proportions of about 0.25 to about 2.5 parts, preferably 0.5 to 1.5 parts by weight. it is preferable also to add 1 to 10 parts of an epoxy compound such as octyl epoxy stearate, epoxidized linseed oil, epoxidized soybean oil, etc., and/or 0.5 to 1.5 parts of a phosphite chelator such as trisnonylphenyl phosphite.

Although the appropriate hydroxy] compounds of the instem invention may be added after polymerization of the vinyl halide monomer, it is preferable to add these materials during the polymerization. The procedure is illustrated by Example 3. Preaddition of appropriate ingredients insures more intimate mixing, thus providing better processability, color clarity and elimination of defects undispersed particles) in the finished article, due to insuflicinet shear during extrusion. Normally,

the additives do not copolymerize with vinyl halide but are The identical compound was then run on a 3-inch mill at 375 nonetheless effective. Alternatively, these ingredients may be F., a temperature 520 F. below that for extrusion-blow added during the blending of the polymerized vinyl halide, molding. This mill temperature was chosen to compensate for preferably at temperatures in the range of the melting point of the greater oxidative effect of the atmosphere during milling. the hydroxy compound in order to insure good blending. 5 Samples were removed from the mill at suitable time intervals.

Processing temperatures for the polymers are generally in The first specimens (taken at 5 minutes and pressed to 0.02 the range of 340 to 400 F., and preferably in the range of inch thickness) showed the following results: about 365 to 390 F. The stabilizing system of the instant in Light transmission 47 my, 82.5-86 vention has been found to impart excellent stability to the Absorbancc M476 "m 008-0065 10 Clarity um 69*72 polymer at these temperatures.

The invention will be further understood by reference to the following description and examples.

Yellowness lndex 7.5-4.5

These data are seen to be in good agreement with those from EXAMPLE I blow molding. it is clear then that dynamic mill stability tests provide a good experimental approach toward determining A good Correlation has shown between the P the characteristics of extrusion-blow molding compounds. formance of a polyvinyl halide compound in a typical extrusion-blow molding operation and a dynamic stability test. This EXAMPLE 2 correlation may be demolstraed by.the fonmving Comparison Tables I and ii, below, illustrate the improved color clarity test Bottles of .polyvmyl. Chlonde holnopolymef were obtained for various vinyl halide polymers by the use of the prepared by a typical extruslon'blow moldmg Operanon the hydroxyl compound stabilizers of the instant invention. In melt temperature of the extrudate being in the range 380 to each case identical calciumqnagnesium zinc Saks were 395 F. Sections of these bottles were then cut out and pressed present L45 p p hundred of resin (phr) and the to 0.02 inch thickness at 365 F. and evaluated for clarity in a hydroxyl additives in 15 p (Table I) and 3 p (Table II). spectrophotometer and for clarity and yellowness index 1n a Resum Obtained are from a dynamic mi stability test using a rcolorim-eter Typical data am asfouows: 3 inch mill at 375 F. Specimens were taken after 5 minutes h A 7 t 476 82 84 (Table I) and l, 2, 3, 4 and 5 minutes (Table II), and pressed i gsgzg z ffl to 0.02 inch thicltness. The polymers used are identified in Clarity (Y 68*72 Table Ill and specific identifying properties set forth. Ycllowness Index 9-5 TABLE I [Eflcct of hydroxyl compounds on initial yellowness] A B C D E 1 Percent Ycllow- Percent Ycllow- Icrccnt Ycllow- Percent Ycllow- Percent Ycllowdecreas ness decrease in ncss decrease in ncss decrease in ncss decrease in ncss in yellowindcx 1 yellowing index 2 yellowing index 2 yellowing index 2 yellowing index ing No liydroxyl compound prcscnt 7. 5 17. 5 16. 5 15 4. 5 l-octadccanol 5. 5 27 11 37 14 15 12 20 Methyl 12-hydroxy stcaratc. 4 47 13 2G 15. 5 6 15 0 2. 0 12-hydr0xy stcaric acid 13 3 1 Contains trace of Dining agent to mask initial yellowing. Samples from mill aitcr 5 minutes.

, 1000.28 Xcrn1.0fi Zorn) 1 As measured by ASTM D1925-G3T. YI= Where It, Y and Z are GIL trrstirnulus values for lcd, green (brightness or You; clarity) and blue, respectively.

Incrcasc.

TABLE 11 llCll'uuL oi liytlroxyl compounds on initial ycllownvss} A A ll l) E l Ycl- Ycl Ycl- Ycllowlcrccnl low- Iurccnt Ycllowlcrccnl; Ycllowlcrccnt low- Poi-cont low- Percent ncss Dccrcasc ncss (increase ncss doercasc ncss dccrcasc ncss dccrcasc ncss dccrcasc index in yclindex in yclindex in yclindex in yclindcx in yclindex in ycl- (avg.) lowing (:ivg.) lowing (avg) lowing (-tivg.) lowing (avgJ lowing (avg.) lowing No liydroxyl compound present. 11! 1 t5 8.5 1-d0dccan0l 8.5 30 7 12 4.5 2-dodccanol 51.5 20 (3.5 1-tctradccanol .1 25 7 12 4 l-octadccanol,. 10 15 5.5 30 4.5 Lcicosanol c 10 15 7.5 5 5 Mcthyla-hydroxy stcaratc H 10.5 12 i0 15 0 Mcthyll2-hydroxy stearatc. 10.5 12 7 12 6.5 Methyl l7-liydroxy stcaratc 11 8 7. 5 5 7. 5 Methyl U, 10-diliydroxy stein-aux... X. 5 30 8. 5 3 5 7.5

TABLE III [Properties of polyvinyl halide resins] PVC homopolymers PVC copolyrners A A 1 B C D E F High High Regular poroslty Regular density Regular Regular Comonomer, wt. percent (2. 7) 3 (2.0) K-value 59. 60 Powder densit 4 0. 62 0. 53 Glass transition temp. 75 72 Particle size:

Medium mm 0.120 0.085 0.084 35 0. 074 Distribution coeflicient. 0.183 0. 664 0.137 96 0.588 Percent retained on- 1 2 parts methyl 12-hydroxy stearate added during polymerization. l Propylene. 3 Allryl vinyl ether.

EXAMPLE 3 600 g. vinyl chloride were charged to an autoclave, along with 1,200 g. water containing dissolved therein [.5 g. hydroxy ethyl cellulose (15,000 M.W.) as suspending agent. Methyl l2-hydroxy stearate (12 g) was added and then 0.8 g 50 percent solution of caprylyl peroxide initiator in toluene. The reaction temperature was 140 F. Initial pressure was 150 psi and polymerization proceeded normally to a final pressure of 70 psi after 3/4 hours. Polymer yield was 90 percent.

Properties of the product are listed under PVC Homopolymer A'of Table 111. Although the K-value (molecular weight) of A'was essentially the same as resin A to which no methyl lZ-hydroxy stearate was added, the glass transin'on temperature of A was lower by 10 C., thus yielding a resin of better processability. In this respect polymer A was superior even to the copolymers E and F of Table III which had glass transition temperatures only 3 and 6 C. lower, respectively, than the homopolymer. Mill test data are included in Tables II and IV.

EXAMPLE 4 The dynamic mill stability test provides additional information of value. By removing samples from the mill at various times during the 5 minute period, under the same conditions as stated previously, and evaluating these samples for color clarity, a continuous measure of the heat stability of various polymers with and without the hydroxy compound stabilizers can be determined. FIGS. 1, 2 and 3 represent plots of the yellowness index of samples milled under the conditions shown above for various time periods. The rate of thermal degradation is given by the slope of the curve at the mid-point 3 minutes. A low value of the slope corresponds to a high degree of operational latitude in processing. This is most desirable in It is clear from the above description and data that not only initial color clarity but dynamic heat stability of vinyl halide polymers (at a constant temperature) were appreciably increased by the use of the stabilizer systems of the instant invention. Although the mechanism is not fully understood, it is due at least in part to the unexpected plasticizing and lubricating effects of the hydroxy additives on the polymer particles at the processing temperature. The effect of the monoalcohols and esters on the glass transition temperature of the polymer and the concomitant lowering of melt viscosity at about the processing temperature, provide 15-25 F. lower stock temperatures in extrusion-blow molding with the result that product color and clarity are even better than predicated by perature lowering (AT,,) generally greater than conventional plasticizers (phthalates). On the other hand, the free hydroxy acids have a negligible effect on the glass transition temperature, and it has been shown that l2-hydroxy stearic acid promotes yellowing and loss of clarity in PVC (Table l), as is also well known in the art for other acids such as stearic and oleic acids.

TABLE V EFFECT OF ADDITIVES ON GLASS TRANSITION TEMPERATURE (m OF PVC HOMOPOLYMERS Lowering of Polymer T, AT, (*C.) Per 5 Parts Additive by Weight Alcohols of Instant Invention practice since a large number of operating variables must be 20 closely controlled. Z-Dodecanol 20 The thenna] stability data based on the slopes of the yelfg ffi m lowness index vs. time curves are summarized in Table IV. Eicosan1 1 l TABLE IV [Eflect of hydroxyl compounds on rate of yellowing] A A B D E I F Percent Percent Percent Percent 7 Percent Pe rcent Slope at decrease Slope at decrease Slope at decrease Slope at decrease Slope at decrease Slope at decrease 3 mins. in slope 3 mins. in slope 3 mins. in slope 3 mins. in slope 3 mins. in slope 3 mins. in slope No hydroxyl compound present 3.2 1.6 0.9 1.7 l-dodeeanol (C12) 2- 2 2. 4 25 1.3 20 1. 2 3 30 1. 7 u 2-dodecanol(C1g) 2.0 25 l-tetradecanol (C14) 1- 0 1. 5 55 2. 0 3 25 1.7 3 85 I-octadecanol (C15)... 2.1 1. 5 55 1. 3 20 0.4 55 1.0 5 l-eicosanol (C20) 1. 9 2. 5 20 1. 1 30 0. 7 20 l. 1 35 Methyl a-hydroxy stearate 2. 3 1. 3 0. 9 40 1. 2 3 3O 1. 5 l0 Methyl IZ-hydroxy steam 1.8 1. 6 50 0. l! 40 1. 1 3 20 0. 8 5!) Methyl 17-hydroxystearate. 1. 1.6 50 1.2 25 Methyl 9,10-dlhydroxy stearate 1.8 2.5 20 1.4 15 1 o a 10 0 '1 45 1 Slope of yellowness index vs. time curve at 3 minutes. Indicates thermal stability under shear. 2 parts ester added before polymerization. 3 Increase.

PAICI'S of Instant Invention Methyl a-Hydroxy Stearate 22 Methyl l2-Hydroxy Stearate 24 Methyl l7-Hydroxy Stearate 22.5

Methyl 9,lO-Dihydroxy Stearate 19 Conventional Plasticizers Di-2-Ethyl Hexyl Phthalate l6 Butyl Benzyl Phthalate 15 Free Acids Hydroxy Stearic Acids 2 M Dihydroxy Stearic Acid CUmOl'lOmCfli of Vinyl Chloride Propylene (Example E) 6 Alkyl Vinyl Ether (Example F) l9 The relationship between plasticizing effect (AT,,) and improvement in heat stability during processing is substantiated by reference to the experimental data on copolymers E and F. The copolymeis already contain plasticizing and lubricating moities propylene and alkyl vinyl ether. Therefore, the effect of the additives of the instant invention is less for copolymers than for homopolymers, though still significant.

While these examples adequately illustrate the invention, it should be understood that the present invention in its broadest aspects is not necessarily limited to the specific materials, conditions and procedures shown therein. The present invention is limited only by the claims which follow.

What is claimed is:

l. A stabilized resin composition which comprises as a major constituent a vinyl halide polymer and as the stabilizing agent a mixture of the calcium, magnesium and zinc salts of organic acids in combination with an ester of a long chain hydroxy acid having the following formula:

wherein X is hydrogen or a C -C straight chain alkyl group, L is C to a C straight chain alkyl group, and M is a C to C alkyl group.

2. The composition of claim 1 wherein the ester is selected from the group consisting of methyl l2-hydroxy stearate, methyl a-hydroxy stearate, methyl l7-hydroxy stearate, and methyl 9, lO-dihydroxy stearate.

3. The composition of claim 1 wherein the vinyl halide polymer is selected from the group consisting of polyvinyl chloride and a vinyl chloride-propylene copolymer wherein vinyl chloride monomer is the major constituent.

4, The composition of claim 1 wherein, measured per parts by weight of polymer, the calcium salt is present in amounts of about 0.01 to about 0.2 parts, the magnesium salt is present in amounts of about 0.1 to about l.0 parts, the zinc salt is present in amounts of about 0.25 to about 2.5 parts by weight and the ester is present in amounts of about I to about 10 parts.

i 1 i i 

2. The composition of claim 1 wherein the ester is selected from the group consisting of methyl 12-hydroxy stearate, methyl Alpha -hydroxy stearate, methyl 17-hydroxy stearate, and methyl 9,10-dihydroxy stearate.
 3. The composition of claim 1 wherein the vinyl halide polymer is selected from the group consisting of polyvinyl chloride and a vinyl chloride-propylene copolymer wherein vinyl chloride monomer is the major constituent.
 4. The composition of claim 1 wherein, measured per 100 parts by weight of polymer, the calcium salt is present in amounts of about 0.01 to about 0.2 parts, the magnesium salt is present in amounts of about 0.1 to about 1.0 parts, the zinc salt is present in amounts of about 0.25 to about 2.5 parts by weight and the ester is present in amOunts of about 1 to about 10 parts. 